This means for your local city or area, there might be some slight differences. The first thing that must be understood is that there is not a nationally accepted definition for active and passive recreation uses within the various states and municipalities thereof. How does this understanding of active and passive recreational use affect mountain biking in urban areas? ![]() But when talking about active or passive recreational uses, what is being referred to? How can one activity be referred to as “active use” and a seemingly similar activity be referred to as “passive use”. Sonar on ships and submarines can do the same, passively listening for other vessels or sending out a “ping” to listen for the echo. ![]() Microscopes can be passively viewing or, like an electron microscope, they can actively view. Some types of instruments can be in either passive or active types. Passive sensors do not emit any energy, but measure the observed item's own emitted energy, again, light waves, sound waves or kinetic means to measure properties of that item. Active sensors use some kind of directed energy, whether that be light waves, sound waves or kinetic means to measure properties about an item. ![]() ![]() In the discussion of scientific instruments and measuring devices, there are two major categories: active sensors and passive sensors.
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